Hand-held relt sander



Feb. 24,1970 D. M. DUNN HAND-HELD BELT snmnn 2 Sheets-Sheet 1 Filed Aug. 14. 1967 INVENTOK JOHN MALCOLM DUNN ATTORNEY Feb. 24, 1970 D. M. DUNN HAND-HELD BELT sman 2 Sheets- Sheet 2 Filed Aug. 14. 196? Ill I a m m a u MW H i a T (F mm V 3 9 m v N .H O .J 4 a v IIYQ 2 l 0 r J g y Z M. 9 6 I F AT TORNE Y 4 United States Patent US. Cl. 51-170 4 Claims ABSTRACT OF THE DISCLOSURE A reciprocating or continuous belt sander or butfer in which a hand-held motor comprises one hand grip from which a sander belt extends. The belt is driven by a pinch roller unit connected to the hand-held motor. A belt guide member is remote from the motor and drive unit. The guide member is maintained at a distance from the motor handle unit, either by a second hand grip carrying the belt guide member or by other spacer means connecting to the motor unit such that varying degrees of belt slack are possible. Mandrels of various shapes removably attached to the sander may back up the reciprocating or continuously moving belt.

BACKGROUND OF THE INVENTION Conventional belt sanders are bench-mounted and the workpiece is brought to, and the work performed against, a taut belt. Similar reciprocating, continuous belt and orbital sanders of a portable nature do exist and fulfill a limited function. However, a portable slack belt sander which may be brought to the work has many advantages. First, a belt sander affording an abrasive belt capable of slack enables such a sander to adapt to varying workpiece configurations, and provides for reversing the belt such that the abrasive surface is within the loop of the belt. Workpieces such as doweling, chair rungs, etc. may then be sanded with the grit side of the belt turned inward.

With equal facility polishing operations may be performed wherein the belt, whether reciprocating or continuous, has a relatively soft surface such as is used in polishing and bufiing various metals, or shoes.

SUMMARY OF THE INVENTION The invention contemplates a belt sander or polisher capable of being hand-held and comprising a combined motor and handle unit with a moving sander or polisher belt. A belt surface drive assembly is adjacent the handle unit. A belt guide member is located remote from the handle unit. A guide member mount is supported by spacer means which maintains the guide member mount at a distance from the belt surface drive assembly to afford a working belt surface of some linear extent.

Various attachments, such as specially shaped mandrels, may also be held by the spacer means or the motor and handle unit.

Belt width may vary from one-eighth of an inch to three or four inches. Abrasive tapes or belts are commercially available in this range of widths. The motor unit may be powered from either AC or DC, battery current, or pneumatic power.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic side view of a reciprocating belt sander or buifer in accordance with the invention;

FIG. 2 is a schematic bottom plan view of the belt device of FIG. 1;

FIG. 3 is a sectional elevation taken along line 33 of FIG. 1;

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FIG. 4 is a schematic side elevation of an alternate embodiment of the invention;

FIG. 5 is a schematic side view of a further alternate embodiment of the invention;

FIG. 6 is a schematic side view of a still further alternate embodiment;

FIG. 7 is a schematic diagram of a further alternate embodiment of the invention having a removable mandrel for special sanding purposes;

FIG. 8 is a schematic diagram of a further alternate embodiment of the invention shown fragmentarily; and

FIG. 9 is a schematic side elevation of an alternate embodiment of the invention utilizing a continuous belt drive.

In the following description the like components are identified by like reference characters.

In the embodiment of FIGS. 1-3 a hand-held sander generally designated 10 comprises a motor and handle unit 11 which supports a sander belt reel 12 in a reel cup 13. The sander belt 14 extends from the cup through a belt surface drive assembly generally indicated at 15 and over a remote guide roller 16 which guides the sander belt. Itis to be understood that the belt referred to can be a buffer belt as well as a sanding belt.

A spool-shaped roller 16 is held by a spacer tongue 17 upon a guide mount pin 18 that extends from a support flange 19 fixed to an end plate 21 of the motor and handle unit. Reel cup 13 may be suspended also by the end plate.

Flange 19 also supports belt surface drive assembly 15. The drive assembly comprises a central feed roller 22 upon which diametrically opposed pinch rollers 23, 24 impinge peripherally. The pinch rollers are pivotally mounted to, and actuated by, a rocker arm 27 which pivots with a flange shaft 28 joumalled in the flange and that passes through the feed roller. Oppositely reciprocating thrust arms 31, 32 connect to the rocker arm on opposite sides of its central pivot point. The thrust arms in turn are actuated by motive power within drive and handle unit 11.

The drive mechanism may be any one of many conventional types, whether rotary or reciprocating, and may be powered by alternating, direct or battery current.

A Working segment 34 of the belt passes about guide roller 16 and between feed roller 22 and pinch roller 24. The end 36 of sander belt 14 may extend a slight distance beyond the periphery of the pinch roller, as shown in FIG. 1.

In operation, the sander belt is caused to reciprocate, as shown by the arrow pairs 37, 38, in response to rocking motion of arm 27. The pinch rollers move between the full line positions shown at 23 and 24 and the broken line positions shown at 23A, 24A. The rocker arm and feed roller move together. Since the axes of feed roller 22 and the rocker arm coincide, the motion of the feed roller is rotative. There is no change in the points of contact of the pinch rollers with the feed roller. Therefore, there is no effective advance of the sander belt from the reel, since the contact of the pinch rollers against the feed roller is sufficient to hold the belt fixed at that point. However, the displacement of the pinch rollers from position 23 to 23A, for instance, causes the sander belt to be pulled about guide roller 16 and then quickly pulled in the opposite direction as the pinch roller changes from position 23A back to position 23 under the urging of thrust arms 31, 32. There is, therefore, a very rapid, short stroke, reciprocation of the sander belt.

As the belt becomes worn it may be advanced from the reel by causing relative peripheral rotation of feed roller 22 with respect to pinch rollers 23, 24. This is accomplished by means of a knurled handle 41 which is fixed to the feed roller. The pinch rollers are secured to their respective shafts 43, 44 by knurled nuts 45.

A saw-edged blade 47 may be fixed to the end flange of the motor and handle unit to sever excess length of the used sander belt as it is fed by roller 22 past pinch roller 24.

Obviously spring roller or other devices of conventional design may be used to reduce slack in the belt between reel 12 and pinch roller 23. The peripheral tension between the pinch rollers and feed roller 22 determines the amount of slack which may be induced in the belt on either side of guide roller 16. Obviously if the Working surface of the belt is outward either segment of the belt on either side of roller 16 may be used for sanding r polishing. It is also apparent that the grip or work surface of the belt may vary with the usage. Coarser grit is used for that work which requires removal of much material. The belt can be of a fine surfaced cloth if a polishing operation is desired.

A mandrel 48 may be secured to spacer tongue 17 by slip fasteners 49, if desired. The mandrel has a back-up plate 51 to support the belt after it passes over roller 16, such that flat sanding may be accomplished by pressing that portion of the belt which is backed by plate 51 against the work.

FIG. 4 illustrates an alternate embodiment of the invention wherein a concave plate 55 is supported by a mandrel 56 on tongue 17 of a sanding unit. The motor drive and handle unit differs from the embodiment of FIG. 1 in that reel 12 of sanding material is housed in 'a recess at the back of a motor case 58. A channel 59 in the case conducts the belt over a bent portion 61 of end plate 21 to the juncture of pinch roller 23 and feed roller 22.

The rocker arm 27 of the embodiment of FIG. 4 carries a single pinch roller 23. The arm is otherwise mounted and actuated the same as in the embodiment of FIG. 1. A second rocker arm 27A is mounted at the end of tongue 17 to guide abrasive belt 14. Second rocker arm 27A supports a second feed roller 22A and a second pinch roller 63. Rocker arm 27A is biased by an extension spring 64 such that it recovers its original position after each reciprocation of sander belt 14 under the urging of rollers 22, 23.

The sander belt is advanced by rotation of bo h feed rollers 22 and 22A by means of their knurled handles 41.

DESCRIPTION OF THE PREFERRED EMBODIMENT The embodiment of FIG. 5 is shown in a fragmentary view which is the obverse of the view of FIG. 4. A motor case 58 which is part of a motor and handle unit 11 is shown fragmentarily. The end plate of the case supports aflange 19 which pivotally mounts a rocker arm 27 with diametrically opposed pinch rollers 23, 24. A feed roller 22 is shown in dotted lines. A sander belt 14 extends from a belt reel (not shown) between feed roller 22 and pinch roller 23 outwardly from the motor and handle unit shown fragmentarily at 11 out across a convex workpiece 67 and around a guide means or spool roller 16. Sander belt 14 then extends back toward the motor and handle unit in a belt segment 34 and passes between feed roller 22 and pinch roller 24.

A guide mount 68 journals a guide roller 16. The guide mount extends from a hand grip bracket 69 which has a cylindrical handle 71. Preferably guide mount 68 has a swivel pin 72 so that the attitude of the handle may be adjusted with respect to the work surface of the sander belt.

The handle bracket is used to maintain guide roller 16 at an interval from motor and handle unit 11. Because there is no rigid spacer between guide roller 16 and drive assembly 15, any desired amount of belt slack may be obtained to permit the belt to fit the configuration of whatever workpiece is being worked upon. The amount of displacement of one sander belt loop from the other may be increa ed by increasing the diameter of guide roller 16. By this means workpiece convexities of various projection may be accommodated.

Shaft 28 of the drive assembly of FIG. 5 has pinned to it a ratchet wheel 75. A ratchet dog 76 engages the teeth of the ratchet wheel. The dog may be spring-loaded by means of leaf, compression or extension springs. As can be seen from FIG. 5, the ratchet wheel, and therefore the feed roller 22 fixed to shaft 28, is free to move in counterclockwise direction in response to actuation of rocker arm 27. However, clockwise rotation of the ratchet wheel and thus roller 22 inhibited by ratchet dog 76. There is, therefore, relative displacement between the feed roller 22 and the pinch rollers 23, 24. Such relative displacement causes the sander belt to feed outwardly from its supply reel (not shown) commensurate with the travel of each pinch roller across the periphery of the feed roller. 7

The proportions and tooth spacing of the ratchet wheel may be modified to accomplish the amount of sander belt feed necessary to retain an efficient grit surface against the workpiece. Means other than the ratchet wheel for feeding the sander belt as it reciprocates are also comprehended by the invention.

FIG. 6 shows an alternate embodiment of the invention similar in concept to FIG. 5. A motor casing 58 of a handle and motor unit 11 supports a flange 19, from which a twin pinch roller and feed roller drive assembly 15 is supported. A guide roller 16 has a protruding shaft 81 which seats in a floating guide means mount 83. The mount resides in an elongate channel in a mounting bracket 84. The bracket supports the flange and motor case in a bracket recess 86 in which the flange and end plate are secured by a conventional screw 87. An extension spring 88 biases guide means mount 83 away from motor and handle unit 11. Belt tension is thus retained or adjusted.

A limit switch '89 is spring-mounted within the channel of bracket 84 between guide means mount 83 and the handle and motor unit. When a workpiece (not shown) is brought into contact with a belt 14, guide roller 16 is moved toward the motor and handle unit against the pressure of spring 88. Sutficient motion of mount 83 causes contact with limit switch 89 which is a normally off switch. The contact actuates the motor of the drive unit and continues it in actuation despite continuing leftward displacement of guide means mount 83 in FIG. 6. When the pressure of a workpiece is removed from the belt spring 88- moves guide roller 16 away from limit switch 89 and turns off the motor. Conventional means such as screws 91 may be used to fasten bracket 84 to a work bench.

Release of the handle motor unit from channel 86 of the bracket and attachment of a handle to shaft 81 permits the embodiment of FIG. 6 to once again become a hand-held sander.

Many other variations of the spacer means of the sander of the invention may be utilized. FiG. 7 shows schematically a hand-held sander 94 wherein a removable rigid spacer 95 connecting between outer guide roller 16 and the handle and motor unit 11 has two spacer segments 97, 98 forming a dihedral angle 99, such that the attitude of belt 14 is changed with respect to the initial extension of the belt from the motor and handle unit. Segment 97 is releasably secured to the handle and motor unit bYrCOH- venient means. Intermediate rollers 98, 99 are supported at the juncture of the two spacer segments. The belt is driven by a reciprocating drive assembly (not shown) similar to the assembly of the embodiment of FIG. 1.

As shown in FIG. '8, spacer segment 98 may receive a removable mandrel or shoe which acts as a back-up plate for belt 14 for use against planar surfaces of a workpiece.

In FIG. 9 a hand-held continuous belt sander comprises a motor and handle unit 111 which has a motor end plate 1 12 upon which a pinch roller 113 is journalled.

The pinch roller is in perpheral contact with a drive roller 115. A continuous sander or buffer belt 118 passes between the pinch roller and the drive roller. The motor casing supports a first hand grip 121 which is adjacent an on-oft switch 122 of the motor.

A U-shaped bracket 123 comprises a spacer means to maintain a guide roller 124 remote from the motor and handle unit. The bracket has a telescoping stern 125. A second hand grip 126 is fixed to a leg of the U-shaped bracket adjacent the guide roller. A compression spring 128 opposes telescoping of the stern. Both the second hand grip and compression spring 128 may be used to bias guide roller 124 away from the motor and handle unit.

A slack take-up roller 129 is pivotally mounted by an arm 131 from the spacer bracket. An extension spring 132 or other similar biasing means may be used to load the roller so as to maintain an inner loop 135 of the sander belt away from an outer loop 136.

The apparatus of FIG. 9 again provides an embodiment wherein the sander or buffer belt may be provided with slack to accommodate the configuration of the workpiece. Workpiece 141 in FIG. is rather abruptly convex. By moving the sander downwardly against the workpiece surface with sufficient force, spring 128 may be overcome sufficiently to give outer loop 136 of the belt enough slack to wrap against the convex surface for polishing or sanding.

The foregoing embodiments are to be regarded as illustrative only. The term abrasive is to be understood as encompassing those belts with surfaces adapted for polishing, bufling, sanding and the like operations. Many other variations within the scope of the invention will occur to those skilled in the particular art. I therefore wish the invention to be measured by the appended claims rather than by the illustrative embodiments disclosed herein.

I claim:

1. A hand-held abrasive belt machine comprising a combined motor and handle unit, an abrasive belt, a belt surface drive assembly adjacent the handle unit; said belt surface drive assembly including a rocker arm, a belt advance roller having an axis coinciding with the pivot axis of the rocker arm, a contact pressure member on the rocker arm bearing peripherally on the belt advance roller, and means linking the rocker arm to the motor for rocking motion about the rocker arm pivot axis; a belt guide member remote from the handle unit, a guide member mount, and spacer means for maintaining the guide member mount at a distance from the belt surface drive assembly.

2. Apparatus in accordance with claim 1 wherein the spacer means and guide member mount comprise a single hand grip carrying a belt guide roller and adapted to be pulled by a user against sander belt tension away from the motor and handle unit.

3. Apparatus in accordance with claim 1 wherein a second contact pressure member is mounted on the rocker arm to bear peripherally against the belt advance roller.

4. Apparatus in accordance with claim 3 wherein the belt passes between the advance roller and a contact pressure member, over the belt guide member and back between the advance roller and the second contact pressure member.

References Cited UNITED STATES PATENTS 2,560,102 7/1951 Guinn 51170.4 X

2,115,812 5/1938 Hardy 51170.4

2,060,266 11/ 1936 Thompson 51170.4

2,647,350 8/1953 Blazak 51135 X 3,335,528 8/1067 Bader 51--170.4 X

FOREIGN PATENTS 1,3 60,286 3/1964 France.

JAMES L. JONES, IR., Primary Examiner Us. 01. X.R. 51-135 UNITED STATES PATENT OFFICE CERTIFICATE OF CGRRECTION Patent No. 3 496 679 Dated February 24, 1970 Inventor(s) JOHN MALCOLM DUNN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE DRAWING:

Sheet 1, line 1, change "D. M; DUNN" to J. M. DUNN- Sheet 2 line 1, change "D. M. DUNN" to J. M. DUNN-- SIGNED AND mum mcmsm Atteat:

Edward MFIeIcher, If. m m

1w 1:. 60mm.

Anesung Officer commissioner bf Patents FORM PO-IOSO (10-59) USCOMM-DC 603764 69 Q u.s. covunutm' rlm'mlo orrlc: "6! 0-ul-s31 

